The present invention relates to user-programmable antifuse devices; more specifically, it relates to combinations of antifuse devices and antifuse heater elements and the method of programming antifuse devices having antifuse heater elements.
An antifuse is a programming device that is essentially an open circuit before programming and a closed circuit after programming. One type of antifuse is a capacitive antifuse. A capacitive antifuse is a structure composed of an insulator with a conductive plate on opposite sides of the insulator. The antifuse is programmed by applying a voltage across the two plates sufficient to break down the insulator between the plates, thus shorting the plates together.
Generally, very high voltages are required to program an antifuse. This presents two problems in applying antifuse technology to advanced semiconductor chips. First, the programming voltage may be so much higher than devices of a semiconductor chip are designed to withstand that damage to the devices results when the antifuses are programmed. Second, in certain applications, the high programming voltage may not be available on the semiconductor chip. The conventional method of overcoming these two problems has been to try to use a lower than ideal voltage for a shorter time. However, this approach results in increased process time and costs as well as decreased reliability in terms of the programmed antifuse staying programmed, i.e. staying shorted and not opening up over the life of the chip, thus causing chip failure in the field.
A first aspect of the present invention is a programmable device comprising: an antifuse; a resistive heating element having a substantially linear temperature to power response, the resistive heating element adjacent to but not in contact with the antifuse; and means for passing an electric current through the resistive heating element in order to generate heat to raise the temperature of the antifuse sufficiently high enough to decrease a programming voltage of the antifuse, a time the programming voltage is applied to the antifuse or both the programming voltage of the antifuse and the time the programming voltage is applied to the antifuse.
A second aspect of the present invention is a method of programming an antifuse comprising: providing an antifuse; providing a resistive heating element having a substantially temperature to power response, the resistive heating element adjacent to but not in contact with the antifuse; passing an electric current through the resistive heating element in order to generate heat to raise the temperature of the antifuse sufficiently high enough to decrease a programming voltage of the antifuse, a time the programming voltage is applied to the antifuse or both the programming voltage of the antifuse and the time the programming voltage is applied to the antifuse; and passing the programming voltage through the antifuse to form an electrically conductive path through the antifuse.